The typical \(\rm [OIII]\)  luminosity of our type II AGN sample
is less than \(10^{41} \rm erg~s^{-1}\) , at which the
type I fraction is less than 20%[1]}, [2]}.
This means that Type Is can only be a small part of the whole AGN sample,
and that the impact of excluding type Is may not be large.
However the selection effects for the two types are
usually different, and different methods
for constructing control samples are adopted in earlier studies.
These make it difficult to estimate the impact of including Type Is.
Moreover, the difference between the two types of AGNs
indicates that they may be triggered by different processes [3]}.
Including type Is may, therefore, mix various effects, making it
more difficult to understand the underlying processes.
Given all of these, we believe that it is better to investigate the
two populations separately.
